matplotlib.path

A module for dealing with the polylines used throughout Matplotlib.

The primary class for polyline handling in Matplotlib is Path. Almost all vector drawing makes use of Paths somewhere in the drawing pipeline.

Whilst a Path instance itself cannot be drawn, some Artist subclasses, such as PathPatch and PathCollection, can be used for convenient Path visualisation.

class matplotlib.path.Path(vertices, codes=None, _interpolation_steps=1, closed=False, readonly=False)[source]

Bases: object

A series of possibly disconnected, possibly closed, line and curve segments.

The underlying storage is made up of two parallel numpy arrays:

  • vertices: an Nx2 float array of vertices
  • codes: an N-length uint8 array of vertex types, or None

These two arrays always have the same length in the first dimension. For example, to represent a cubic curve, you must provide three vertices as well as three codes CURVE3.

The code types are:

  • STOP1 vertex (ignored)
    A marker for the end of the entire path (currently not required and ignored)
  • MOVETO1 vertex
    Pick up the pen and move to the given vertex.
  • LINETO1 vertex
    Draw a line from the current position to the given vertex.
  • CURVE31 control point, 1 endpoint
    Draw a quadratic Bezier curve from the current position, with the given control point, to the given end point.
  • CURVE42 control points, 1 endpoint
    Draw a cubic Bezier curve from the current position, with the given control points, to the given end point.
  • CLOSEPOLY1 vertex (ignored)
    Draw a line segment to the start point of the current polyline.

If codes is None, it is interpreted as a MOVETO followed by a series of LINETO.

Users of Path objects should not access the vertices and codes arrays directly. Instead, they should use iter_segments or cleaned to get the vertex/code pairs. This helps, in particular, to consistently handle the case of codes being None.

Some behavior of Path objects can be controlled by rcParams. See the rcParams whose keys start with 'path.'.

Note

The vertices and codes arrays should be treated as immutable -- there are a number of optimizations and assumptions made up front in the constructor that will not change when the data changes.

Create a new path with the given vertices and codes.

Parameters:
verticesarray-like

The (N, 2) float array, masked array or sequence of pairs representing the vertices of the path.

If vertices contains masked values, they will be converted to NaNs which are then handled correctly by the Agg PathIterator and other consumers of path data, such as iter_segments().

codesarray-like or None, optional

n-length array integers representing the codes of the path. If not None, codes must be the same length as vertices. If None, vertices will be treated as a series of line segments.

_interpolation_stepsint, optional

Used as a hint to certain projections, such as Polar, that this path should be linearly interpolated immediately before drawing. This attribute is primarily an implementation detail and is not intended for public use.

closedbool, optional

If codes is None and closed is True, vertices will be treated as line segments of a closed polygon. Note that the last vertex will then be ignored (as the corresponding code will be set to CLOSEPOLY).

readonlybool, optional

Makes the path behave in an immutable way and sets the vertices and codes as read-only arrays.
CLOSEPOLY = 79
CURVE3 = 3
CURVE4 = 4
LINETO = 2
MOVETO = 1
NUM_VERTICES_FOR_CODE = {0: 1, 1: 1, 2: 1, 3: 2, 4: 3, 79: 1}

A dictionary mapping Path codes to the number of vertices that the code expects.

STOP = 0
classmethod arc(theta1, theta2, n=None, is_wedge=False)[source]

Return the unit circle arc from angles theta1 to theta2 (in degrees).

theta2 is unwrapped to produce the shortest arc within 360 degrees. That is, if theta2 > theta1 + 360, the arc will be from theta1 to theta2 - 360 and not a full circle plus some extra overlap.

If n is provided, it is the number of spline segments to make. If n is not provided, the number of spline segments is determined based on the delta between theta1 and theta2.

classmethod circle(center=(0.0, 0.0), radius=1.0, readonly=False)[source]

Return a Path representing a circle of a given radius and center.

Parameters:
center(float, float), default: (0, 0)

The center of the circle.

radiusfloat, default: 1

The radius of the circle.

readonlybool

Whether the created path should have the "readonly" argument set when creating the Path instance.

Notes

The circle is approximated using 8 cubic Bezier curves, as described in

cleaned(transform=None, remove_nans=False, clip=None, quantize=<deprecated parameter>, simplify=False, curves=False, stroke_width=1.0, snap=False, sketch=None)[source]

Return a new Path with vertices and codes cleaned according to the parameters.

See also

Path.iter_segments
for details of the keyword arguments.
clip_to_bbox(bbox, inside=True)[source]

Clip the path to the given bounding box.

The path must be made up of one or more closed polygons. This algorithm will not behave correctly for unclosed paths.

If inside is True, clip to the inside of the box, otherwise to the outside of the box.

code_type

alias of numpy.uint8

property codes

The list of codes in the Path as a 1-D numpy array. Each code is one of STOP, MOVETO, LINETO, CURVE3, CURVE4 or CLOSEPOLY. For codes that correspond to more than one vertex (CURVE3 and CURVE4), that code will be repeated so that the length of self.vertices and self.codes is always the same.

contains_path(path, transform=None)[source]

Return whether this (closed) path completely contains the given path.

If transform is not None, the path will be transformed before checking for containment.

contains_point(point, transform=None, radius=0.0)[source]

Return whether the (closed) path contains the given point.

Parameters:
point(float, float)

The point (x, y) to check.

transformmatplotlib.transforms.Transform, optional

If not None, point will be compared to self transformed by transform; i.e. for a correct check, transform should transform the path into the coordinate system of point.

radiusfloat, default: 0

Add an additional margin on the path in coordinates of point. The path is extended tangentially by radius/2; i.e. if you would draw the path with a linewidth of radius, all points on the line would still be considered to be contained in the area. Conversely, negative values shrink the area: Points on the imaginary line will be considered outside the area.
Returns:
bool
contains_points(points, transform=None, radius=0.0)[source]

Return whether the (closed) path contains the given point.

Parameters:
points(N, 2) array

The points to check. Columns contain x and y values.

transformmatplotlib.transforms.Transform, optional

If not None, points will be compared to self transformed by transform; i.e. for a correct check, transform should transform the path into the coordinate system of points.

radiusfloat, default: 0.

Add an additional margin on the path in coordinates of points. The path is extended tangentially by radius/2; i.e. if you would draw the path with a linewidth of radius, all points on the line would still be considered to be contained in the area. Conversely, negative values shrink the area: Points on the imaginary line will be considered outside the area.
Returns:
length-N bool array
copy()

Return a shallow copy of the Path, which will share the vertices and codes with the source Path.

deepcopy(memo=None)

Return a deepcopy of the Path. The Path will not be readonly, even if the source Path is.

get_extents(transform=None, **kwargs)[source]

Get Bbox of the path.

Parameters:
transformmatplotlib.transforms.Transform, optional

Transform to apply to path before computing extents, if any.

**kwargs

Forwarded to iter_bezier.
Returns:
matplotlib.transforms.Bbox

The extents of the path Bbox([[xmin, ymin], [xmax, ymax]])
static hatch(hatchpattern, density=6)[source]

Given a hatch specifier, hatchpattern, generates a Path that can be used in a repeated hatching pattern. density is the number of lines per unit square.

interpolated(steps)[source]

Return a new path resampled to length N x steps.

Codes other than LINETO are not handled correctly.

intersects_bbox(bbox, filled=True)[source]

Return whether this path intersects a given Bbox.

If filled is True, then this also returns True if the path completely encloses the Bbox (i.e., the path is treated as filled).

The bounding box is always considered filled.

intersects_path(other, filled=True)[source]

Return whether if this path intersects another given path.

If filled is True, then this also returns True if one path completely encloses the other (i.e., the paths are treated as filled).

iter_bezier(**kwargs)[source]

Iterate over each bezier curve (lines included) in a Path.

Parameters:
**kwargs

Forwarded to iter_segments.
Yields:
Bmatplotlib.bezier.BezierSegment

The bezier curves that make up the current path. Note in particular that freestanding points are bezier curves of order 0, and lines are bezier curves of order 1 (with two control points).

codePath.code_type

The code describing what kind of curve is being returned. Path.MOVETO, Path.LINETO, Path.CURVE3, Path.CURVE4 correspond to bezier curves with 1, 2, 3, and 4 control points (respectively). Path.CLOSEPOLY is a Path.LINETO with the control points correctly chosen based on the start/end points of the current stroke.
iter_segments(transform=None, remove_nans=True, clip=None, snap=False, stroke_width=1.0, simplify=None, curves=True, sketch=None)[source]

Iterate over all curve segments in the path.

Each iteration returns a pair (vertices, code), where vertices is a sequence of 1-3 coordinate pairs, and code is a Path code.

Additionally, this method can provide a number of standard cleanups and conversions to the path.

Parameters:
transformNone or Transform

If not None, the given affine transformation will be applied to the path.

remove_nansbool, optional

Whether to remove all NaNs from the path and skip over them using MOVETO commands.

clipNone or (float, float, float, float), optional

If not None, must be a four-tuple (x1, y1, x2, y2) defining a rectangle in which to clip the path.

snapNone or bool, optional

If True, snap all nodes to pixels; if False, don't snap them. If None, snap if the path contains only segments parallel to the x or y axes, and no more than 1024 of them.

stroke_widthfloat, optional

The width of the stroke being drawn (used for path snapping).

simplifyNone or bool, optional

Whether to simplify the path by removing vertices that do not affect its appearance. If None, use the should_simplify attribute. See also rcParams["path.simplify"] (default: True) and rcParams["path.simplify_threshold"] (default: 0.111111111111).

curvesbool, optional

If True, curve segments will be returned as curve segments. If False, all curves will be converted to line segments.

sketchNone or sequence, optional

If not None, must be a 3-tuple of the form (scale, length, randomness), representing the sketch parameters.
classmethod make_compound_path(*args)[source]

Make a compound path from a list of Path objects. Blindly removes all Path.STOP control points.

classmethod make_compound_path_from_polys(XY)[source]

Make a compound path object to draw a number of polygons with equal numbers of sides XY is a (numpolys x numsides x 2) numpy array of vertices. Return object is a Path

(Source code, png, pdf)

../_images/histogram_path_00_00.png
property readonly

True if the Path is read-only.

property should_simplify

True if the vertices array should be simplified.

property simplify_threshold

The fraction of a pixel difference below which vertices will be simplified out.

to_polygons(transform=None, width=0, height=0, closed_only=True)[source]

Convert this path to a list of polygons or polylines. Each polygon/polyline is an Nx2 array of vertices. In other words, each polygon has no MOVETO instructions or curves. This is useful for displaying in backends that do not support compound paths or Bezier curves.

If width and height are both non-zero then the lines will be simplified so that vertices outside of (0, 0), (width, height) will be clipped.

If closed_only is True (default), only closed polygons, with the last point being the same as the first point, will be returned. Any unclosed polylines in the path will be explicitly closed. If closed_only is False, any unclosed polygons in the path will be returned as unclosed polygons, and the closed polygons will be returned explicitly closed by setting the last point to the same as the first point.

transformed(transform)[source]

Return a transformed copy of the path.

See also

matplotlib.transforms.TransformedPath
A specialized path class that will cache the transformed result and automatically update when the transform changes.
classmethod unit_circle()[source]

Return the readonly Path of the unit circle.

For most cases, Path.circle() will be what you want.

classmethod unit_circle_righthalf()[source]

Return a Path of the right half of a unit circle.

See Path.circle for the reference on the approximation used.

classmethod unit_rectangle()[source]

Return a Path instance of the unit rectangle from (0, 0) to (1, 1).

classmethod unit_regular_asterisk(numVertices)[source]

Return a Path for a unit regular asterisk with the given numVertices and radius of 1.0, centered at (0, 0).

classmethod unit_regular_polygon(numVertices)[source]

Return a Path instance for a unit regular polygon with the given numVertices such that the circumscribing circle has radius 1.0, centered at (0, 0).

classmethod unit_regular_star(numVertices, innerCircle=0.5)[source]

Return a Path for a unit regular star with the given numVertices and radius of 1.0, centered at (0, 0).

property vertices

The list of vertices in the Path as an Nx2 numpy array.

classmethod wedge(theta1, theta2, n=None)[source]

Return the unit circle wedge from angles theta1 to theta2 (in degrees).

theta2 is unwrapped to produce the shortest wedge within 360 degrees. That is, if theta2 > theta1 + 360, the wedge will be from theta1 to theta2 - 360 and not a full circle plus some extra overlap.

If n is provided, it is the number of spline segments to make. If n is not provided, the number of spline segments is determined based on the delta between theta1 and theta2.

See Path.arc for the reference on the approximation used.

matplotlib.path.get_path_collection_extents(master_transform, paths, transforms, offsets, offset_transform)[source]

Given a sequence of Paths, Transforms objects, and offsets, as found in a PathCollection, returns the bounding box that encapsulates all of them.

Parameters:
master_transformTransform

Global transformation applied to all paths.

pathslist of Path
transformslist of Affine2D
offsets(N, 2) array-like
offset_transformAffine2D

Transform applied to the offsets before offsetting the path.

Notes

The way that paths, transforms and offsets are combined follows the same method as for collections: Each is iterated over independently, so if you have 3 paths, 2 transforms and 1 offset, their combinations are as follows:

(A, A, A), (B, B, A), (C, A, A)